Shooter Identified in Fort Hood Mass Shooting

Fort Hood shooter Ivan Specialist Ivan Lopez went from one building at the sprawling Texas military base to a second, firing a .45 caliber handgun -- killing three people and wounding 16 more. Lopez was part of the National Guard in Puerto Rico, National Guard spokeswoman Ruth Diaz said Thursday. Then the 34-year-old Iraq vet put the gun to his head and pulled the trigger, ending his life and taking with him the reasons for his action.

"There are initial reports there may have been an argument in one of the unit areas," Lt. Gen Mark Milley, the post's commanding general, told reporters late Wednesday.

Officers picked up Lopez' wife at their apartment near the base in Killeen, and she was cooperating with law enforcement, an FBI official told CNN.

The man, whom a neighbor said often gave her a friendly wave, was plagued by multiple mental health issues.

Lopez was new on the base, having only arrived there in February. He, his wife and their small daughter moved into their apartment a little more than a week before the shooting.

They were a normal couple, said neighbor Xanderia Morris. "They would smile whenever they'd see someone," she said.

He served for four months in Iraq in 2011. And while army records don't show him as having been wounded there, Lopez himself reported that he had suffered a traumatic brain injury, Milley said.

He was undergoing diagnosis procedures for Post-Traumatic Stress Disorder (PTSD).

"He was not diagnosed, as of today, with PTSD," Milley said.

Arriving at the diagnosis of the mental ailment that plagues so many war veterans takes time.

Lopez carried out the killings with a privately owned gun -- a .45 caliber Smith and Wesson semiautomatic pistol he purchased after arriving in Killeen.

When he took it onto the base, he was breaking the rules.

"If you have weapons and you're on base, it's supposed to be registered on base," Milley said. "This weapon was not registered on base."

In addition, people are not allowed to walk around with guns on a military base. They are required to store them in a secured armory.

The exact sequence of events is not entirely clear. But around 4 p.m., Lopez walked into a building at the base and opened fire. He then got into a car, fired from the vehicle, walked into another building and fired again.

He killed three and wounded 16 -- all of them were army personnel.

Three of the wounded remained in critical condition early Thursday morning.

Authorities could not say whether Lopez knew his victims.

The shootings took place in the medical brigade and the transportation battalion buildings. Lopez was assigned to the 13th sustainment command, which deals with the logistical responsibilities for the post.

The spree went on for about 15 to 20 minutes, Milley said.

The base housing more than 45,000 soldiers and nearly 9,000 civilian employees went on lockdown.